The present invention relates to the improvements of a control apparatus for an internal combustion engine with a pair of intake valves for each engine cylinder, and particularly to such a control apparatus for the cooperative control of intake-air control and fuel-injection control.
An internal combustion engine equipped with a pair of intake valves for each engine cylinder has been disclosed in Japanese Patent Provisional Publication No. 4-94433. In the engine disclosed in the Japanese Patent Provisional Publication No. 4-94433, in low engine speed ranges one of a pair of intake valves is held in a substantial inactive state and kept slightly opened to such a very small opening that the intake valve pauses at its substantially closed position, and additionally a fuel injector is provided to uniformly inject fuel spray toward both of two intake ports associated with the respective intake valves. Therefore, it is possible to create a great gas flow (increased turbulence) in the engine cylinder, by holding the one intake valve at the previously-described substantial inactive state.
However, in case of an internal combustion engine with a pair of intake valves for each cylinder, fuel would be injected into two intake ports associated with the respective intake valves, even during one-intake-valve operating mode during which one of the pair of intake valves is held at its substantial inactive state. In this case, there is a problem of undesired wall wetting at the intake port kept in the substantial inactive state. That is to say, a flow rate of fuel adhered to the inner wall surface of the intake port, which flow rate will be hereinafter referred to as a xe2x80x9cwall fuel mass flow ratexe2x80x9d, tends to increase. There is a difficulty in forming uniform air/fuel mixture in the engine cylinder (or combustion chamber), and thus the transient air/fuel mixture ratio control accuracy tends to be lowered. As a consequence, exhaust emission control performance is also degraded. Additionally, there is a difference in intake-air velocity between a one-intake-valve operating mode during which one of a pair of intake valves is held at its substantial inactive state and the other intake valve is operated depending on engine operating conditions, and a two-intake-valve operating mode during which the pair of intake valves are both operated depending on the engine operating conditions. The difference in intake-air velocity results in a difference in the wall fuel mass flow rate. Thus, it is desirable to enhance the transient A/F control accuracy by compensating for a fuel injection amount, taking account of the difference in the wall fuel mass flow rate between the two different intake valve operating modes.
Accordingly, it is an object of the invention to provide a control apparatus for an internal combustion engine, which avoids the aforementioned disadvantages.
It is another object of the invention to provide a control apparatus for an internal combustion engine, which ensures increased gas flow within an engine cylinder in a low engine load range, and maintain a high air/fuel ratio control accuracy even during a load change transient.
In order to accomplish the aforementioned and other objects of the present invention, a control apparatus for an internal combustion engine comprises a control apparatus for an internal combustion engine comprises a pair of intake ports provided for each cylinder of the engine, a mode selector which selects, depending on engine operating conditions, either one of a first operating range in which air is drawn into the cylinder only through a first one of the intake ports and a second operating range in which air is drawn into the cylinder through both the intake ports, a fuel injector located in the first intake port through which air flows in all of the first and second operating ranges, and a compensator which switches a compensating mode for an injection amount of fuel injected by the injector, based on changes in a quantity of wall fuel mass flow adhered onto an inner wall surface of each of the intake ports during transient operating conditions, from one of a first compensating mode which is preprogrammed to be suitable for the first operating range and a second compensating mode which is preprogrammed to be suitable for the second operating range to the other.
According to another aspect of the invention, a control apparatus for an internal combustion engine comprises a pair of intake ports provided for each cylinder of the engine, a pair of intake valves located in the intake ports respectively, a mode selecting means for selecting, depending on engine operating conditions, either one of a one-intake-valve operating mode in which a first one of the intake valves is opened during intake stroke and the second intake valve is kept in a closed state so that air is drawn into the cylinder only through a first one of the intake ports and a two-intake-valve operating mode in which the intake valves are both opened during the intake stroke so that air is drawn into the cylinder through both the intake ports, a fuel injector located in the first intake port through which air flows in all of the one-intake-valve operating mode and the two-intake-valve operating mode, and a compensating means for switching a compensating mode for an injection amount of fuel injected by the injector, based on changes in a quantity of wall fuel mass flow adhered onto an inner wall surface of each of the intake ports during transient operating conditions, from one of a first compensating mode which is preprogrammed to be suitable for the one-intake-valve operating mode and a second compensating mode which is preprogrammed to be suitable for the two-intake-valve operating mode to the other.
According to a still further aspect of the invention, a method for controlling an internal combustion engine, wherein the engine includes a pair of intake ports provided for each cylinder of the engine, a pair of intake valves located in the intake ports respectively, and a fuel injector located in a first one of the intake ports to allow air to flow through the first intake port over all operating ranges of the engine, the method comprises selecting, depending on engine operating conditions, either one of a one-intake-valve operating mode in which a first one of the intake valves is opened during intake stroke and the second intake valve is kept in a closed state so that air is drawn into the cylinder only through the first intake port and a two-intake-valve operating mode in which the intake valves are both opened during the intake stroke so that air is drawn into the cylinder through both the intake ports, and switching a compensating mode for an injection amount of fuel injected by the injector, based on changes in a quantity of wall fuel mass flow adhered onto an inner wall surface of each of the intake ports during transient operating conditions, from one of a first compensating mode which is preprogrammed to be suitable for the one-intake-valve operating mode and a second compensating mode which is preprogrammed to be suitable for the two-intake-valve operating mode to the other.